[Optimize preparation of compound licorice microemulsion with D-optimal design]

Area of Science:

• Pharmaceutical Sciences
• Formulation Development
• Dermatology

Background:

• Traditional decoctions often have poor solubility and bioavailability of active compounds.
• Chronic eczema treatment requires effective delivery systems for herbal extracts.
• Microemulsions offer improved solubility and skin penetration for active ingredients.

Purpose of the Study:

• To prepare and optimize a microemulsion formulation of compound licorice extract.
• To enhance the solubility and skin retention of essential oils and active compounds.
• To investigate the in vitro release behavior and efficacy for chronic eczema treatment.

Main Methods:

• Pseudo-ternary phase diagrams were used to determine microemulsion regions and optimal surfactant/cosurfactant ratios.
• D-optimal design methodology was employed for microemulsion prescription optimization.
• Particle size, skin retention, viscosity, stability, and in vitro release kinetics were evaluated.

Main Results:

• An optimal microemulsion formulation was achieved using Tween-80 as surfactant and anhydrous ethanol as cosurfactant.
• The optimal formulation (9.4% Tween-80, 9.4% anhydrous ethanol, 1.0% peppermint oil, 80.2% extract) exhibited low viscosity, good stability, and high skin retention.
• In vitro release studies confirmed a sustained-release effect on glycyrrhizic acid and liquiritin.

Conclusions:

• The developed microemulsion significantly improves the solubility and delivery of compound licorice extract.
• The formulation demonstrates potential for enhanced efficacy in treating chronic eczema due to sustained drug release.
• This microemulsion system provides a promising approach for improving the therapeutic application of herbal decoctions.